Flexible organic electroluminescent device and method for fabricating the same

ABSTRACT

A flexible organic electroluminescent device and a method for fabricating the same includes a substrate defined with a display area including a plurality of pixel regions and a non-display area at the outside thereof; a switching thin film transistor and a drive thin film transistor formed at the each pixel region on the substrate; an organic insulating layer deposited on the substrate including the switching thin film transistor and drive thin film transistor to expose a drain electrode of the drive thin film transistor; a first electrode formed in each pixel region on the inorganic insulating layer, and connected to the drain electrode of the drive thin film transistor; banks formed around each pixel region on the substrate including the first electrode and separated from one another; an organic light emitting layer separately formed for each pixel region on the first electrode; a second electrode formed on an entire surface of the display area on the organic light emitting layer; and an organic layer formed on an entire surface of the substrate including the second electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Korean PatentApplication No. 10-2012-0122697, filed on Oct. 31, 2012, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to an organic electroluminescent device(hereinafter, referred to as an “OLED”), and more particularly, to aflexible organic electroluminescent device for blocking moisture frombeing infiltrated into the organic electroluminescent device to enhancethe life of the organic electroluminescent device, and a method forfabricating the same.

2. Description of the Related Art

An organic electroluminescent device, which is one of types of flatpanel displays (FPDs), has high brightness and low operation voltagecharacteristics. Furthermore, the organic electroluminescent device hasa high contrast ratio because of being operated as a self-luminous typedisplay that spontaneously emits light, and allows the implementation ofan ultra-thin display. The organic light-emitting diode also hasadvantages such as facilitating the implementation of moving imagesusing a response time of several microseconds (has), having nolimitation in viewing angle, having stability even at low temperatures,and being driven at low voltages between DC 5 to 15 V, thus facilitatingthe fabrication and design of a driving circuit thereof.

Furthermore, the fabrication process of the organic electroluminescentdevice can be carried out using only deposition and encapsulationequipment, and therefore the fabrication process is very simple.

The organic light-emitting diode having such characteristics can belargely divided into a passive matrix type and an active matrix type,and in the passive matrix type, a device may be configured with a matrixform in which the scan and signal lines are crossed with each other, andthe scan lines are sequentially driven as time passes to drive eachpixel, and thus instantaneous brightness as much as average brightnessmultiplied by the number of lines may be required to display the averagebrightness.

However, the active matrix type has a structure in which thin-filmtransistors, which are switching devices for turning on or off a pixelregion, are located for each pixel region, and drive transistorsconnected to the switching transistors are connected to a power line andorganic light emitting diodes, and formed for each pixel region.

Here, a first electrode connected to the drive transistor may be turnedon or off in the pixel region unit, and a second electrode facing thefirst electrode may perform the role of a common electrode, therebyimplementing an organic light emitting diode along with an organic lightemitting layer interposed between the two electrodes.

In the active matrix type having such characteristics, a voltage appliedto the pixel region may be charged at a storage capacitance (Cst), andapplied until the next frame signal is applied and thus continuouslydriven for one screen regardless of the number of scan lines.

Accordingly, the same brightness can be obtained even if a low currentis applied, thereby having an advantage of providing low powerconsumption, fine pitch and large screen sized display, and thus inrecent years, active matrix type organic electroluminescent devices havebeen widely used.

The fundamental structure and operating characteristics of such anactive matrix type organic electroluminescent device will be describedbelow with reference to the accompanying drawings.

FIG. 1 is a circuit diagram for one pixel region in a typical activematrix type organic electroluminescent device.

Referring to FIG. 1, one pixel region of a typical active matrix typeorganic electroluminescent device 10 may include a switching thin filmtransistor (STr), a drive thin film transistor (DTr), a storagecapacitor (Cst), and an organic light emitting diode (E).

A gate line (GL) is formed in the first direction, and a data line (DL)disposed in the second direction crossed with the first direction todefine a pixel region (P) along with the gate line (GL) is formed, and apower line (PL) separated from the data line (DL) to apply a powervoltage is formed.

A switching thin film transistor (STr) is formed at a portion where thedata line (DL) and gate line (GL) are crossed with each other, and adrive thin film transistor (DTr) electrically connected to the switchingthin film transistor (STr) is formed within the each pixel region (P).

The drive thin film transistor (DTr) is electrically connected to theorganic light emitting diode (E). In other words, a first electrode,which is one side terminal of the organic light emitting diode (E), isconnected to a drain electrode of the drive thin film transistor (DTr),and a second electrode, which is the other terminal thereof, isconnected to the power line (PL). Here, the power line (PL) transfers apower voltage to the organic light emitting diode (E). Furthermore, astorage capacitor (Cst) is formed between a gate electrode and a sourceelectrode of the drive thin film transistor (DTr).

Accordingly, when a signal is applied through the gate line (GL), theswitching thin film transistor (STr) is turned on, and the signal of thedata line (DL) is transferred to the gate electrode of the drive thinfilm transistor (DTr) to turn on the drive thin film transistor (DTr),thereby emitting light through the organic light emitting diode (E).Here, when the drive thin film transistor (DTr) is in a turned-on state,the level of a current flowing through the organic light emitting diode(E) from the power line (PL) is determined, and due to this, the organiclight emitting diode (E) may implement a gray scale, and the storagecapacitor (Cst) may perform the role of constantly maintaining the gatevoltage of the drive thin film transistor (DTr) when the switching thinfilm transistor (STr) is turned off, thereby allowing the level of acurrent flowing through the organic light emitting diode (E) to beconstantly maintained up to the next frame even when the switching thinfilm transistor (STr) is in an off state.

FIG. 2 is a plan view schematically illustrating a plurality ofsub-pixel regions of an organic electroluminescent device according tothe related art, as a schematic view showing moisture being infiltratedthrough one sub-pixel region and diffused up to adjoining sub-pixelregions.

FIG. 3 is a schematic cross-sectional view of an organicelectroluminescent device according to the related art.

FIG. 4 is a schematic enlarged cross-sectional view of an organicelectroluminescent device according to the related art, as an enlargedcross-sectional view schematically illustrating moisture infiltratedthrough a bank being diffused along the bank.

Referring to FIG. 2, in an organic electroluminescent device 10according to the related art, a display area (AA) is defined on asubstrate 11, and a non-display area (NA) is defined at the outside ofthe display area (AA), and a plurality of pixel regions (P), eachdefined as a region surrounded by the gate line (not shown) and the dataline (not shown) are provided, and the power line (not shown) isprovided in parallel to the data line (not shown) in the display area(AA).

A switching thin film transistor (STr) (not shown) and a drive thin filmtransistor (DTr) (not shown) are formed in the plurality of pixelregions (SP), respectively, and connected to the drive thin filmtransistor (DTr).

In the organic electroluminescent device 10 according to the relatedart, the substrate 11 formed with the drive thin film transistor (DTr)and organic light emitting diode (E) is encapsulated by a passivationlayer (not shown).

Specifically describing the organic electroluminescent device 10according to the related art, as illustrated in FIG. 3, the display area(AA) is defined, and the non-display area (NA) is defined at the outsideof the display area (AA) on the substrate 11, and a plurality of pixelregions (P), each defined as a region surrounded by the gate line (notshown) and the data line (not shown) are provided, and the power line(not shown) is provided in parallel to the data line (not shown) in thedisplay area (AA).

An insulation material, for example, a buffer layer (not shown) formedof silicon oxide (SiO₂) or silicon nitride (NiNx), which is an inorganicinsulation material, is provided on the substrate 11.

A semiconductor layer 13 made of pure polysilicon to correspond to thedrive region (not shown) and switching region (not shown), respectively,and comprised of a first region 13 a forming a channel at the centralportion thereof and second regions 13 b and 13 c in which a highconcentration of impurities are doped at both lateral surfaces of thefirst region 13 a is formed at each pixel region (SP) within the displayarea (AA) at an upper portion of the buffer layer (not shown).

A gate insulating layer 15 is formed on the buffer layer (not shown)including the semiconductor layer 13, and the drive region (not shown)and switching region (not shown) are provided on the gate insulatinglayer 15, and thus a gate electrode 17 is formed to correspond to thefirst region 13 a of each of the semiconductor layer 13.

A gate line (not shown) connected to a gate electrode (not shown) formedin the switching region (not shown) and extended in one direction isformed on the gate insulating layer 15.

An interlayer insulating layer 19 is formed on an entire surface of thedisplay area on the gate electrode 17 and gate line (not shown). Asemiconductor layer contact hole (not shown) for exposing the secondregions 13 b and 13 c, respectively, located at both lateral surfaces ofthe first region 13 a of each of the semiconductor layer, is provided onthe interlayer insulating layer 19 and the gate insulating layer 15 at alower portion thereof.

A data line (not shown) crossed with a gate line (not shown) to definethe pixel region (SP) and formed of a second metal material, and a powerline (not shown) separated therefrom are formed at an upper portion ofthe interlayer insulating layer 19 including the semiconductor layercontact hole (not shown). Here, the power line (not shown) may be formedto be separated from and in parallel to the gate line (not shown) on alayer formed with the gate line (not shown), namely, the gate insulatinglayer.

A source electrode 23 a and a drain electrode 23 b brought into contactwith the second regions 13 b and 13 c separated from each other, andrespectively exposed through the semiconductor layer contact hole (notshown) and formed of the same second metal material as that of the dataline (not shown) are formed in the each drive region (not shown) andswitching region (not shown) on the interlayer insulating layer 19.Here, the semiconductor layer and gate insulating layer sequentiallydeposited on the drive region (not shown) and the gate electrode 17 andinterlayer insulating layer 19 and the source electrode 23 a and drainelectrode 23 b formed to be separated from each other forms a drive thinfilm transistor (DTr).

An organic insulating layer 25 having a drain contact hole (not shown)for exposing the drain electrode 23 b of the drive thin film transistor(DTr) is formed on the drive thin film transistor (DTr) and switchingthin film transistor (not shown).

A first electrode 31 brought into contact with the drain contact hole(not shown) through the drain electrode 23 b and the drain contact hole(not shown) of the drive thin film transistor (DTr) and having aseparated form for each pixel region (SP) is formed on the organicinsulating layer 25.

A bank 33 formed to divide each pixel region (SP) is formed on the firstelectrode 31. Here, the bank 33 is disposed between adjoining pixelregions (SPs).

An organic light emitting layer 35 comprised of organic light emittingpatterns (not shown) for emitting red, green and blue colors,respectively, is formed on the first electrode 31 within each of thepixel region (SP) surrounded by the bank 33.

A second electrode 37 is formed on an entire surface of the display area(AA) at an upper portion of the organic light emitting layer 35 and bank33. Here, the first electrode 31 and second electrode 37 and the organiclight emitting layer 35 interposed between the two electrodes 31 and 37form an organic light emitting diode (E).

A first passivation layer 39 is formed on an entire surface of thesubstrate including the second electrode 37.

A high organic molecular substance such as a polymer is coated over thefirst passivation layer 39 to form an organic layer 41.

A second passivation layer 43 is additionally formed on an entiresurface of the substrate including the organic layer 41 to blockmoisture from being infiltrated through the organic layer 41.

Moreover, though not shown in the drawing, an adhesive is located on anentire surface of the substrate including the second passivation layer43 to face a barrier film (not shown) for the encapsulation of theorganic light emitting diode (E), and the adhesive (not shown) iscompletely glued to the substrate 11 and barrier film (not shown) andinterposed between the substrate 11 and barrier film (not shown).

In this manner, the organic electroluminescent device 10 according tothe related art is configured by fixing the substrate 101 to the barrierfilm (not shown) through the adhesive (not shown) to form a panel state.

As described above, according to an organic electroluminescent deviceaccording to the related art, when there exists a defect in the barrierfilm (not shown) for encapsulation as illustrated in FIGS. 2 and 4,moisture is infiltrated into the pixel region (SP) through the defectand the organic insulating layer 25 which is a planarization layer orinfiltrated into the pixel region (SP) through the defect and the bank33. In particular, when moisture is infiltrated through the bank 33, themoisture is diffused along the bank 33, which is an organic material,thereby causing all the adjoining pixel regions (SPs) to be defectivesince the bank 33 is adjacent to the adjoining pixel regions (SPs).

According to the related art, when a planarization layer, namely, anorganic insulating layer, is not formed in the non-display area to blockmoisture from being infiltrated into the pixel region (SP) through thedefect or planarization layer, it may cause deteriorate the quality dueto a step at the inorganic layer or the like disposed on the organicelectroluminescent device.

In addition, according to the related art, even when the bank is dividedto block moisture from being infiltrated into the pixel region (SP)through the defect or planarization layer, the moisture may be diffusedthrough an organic insulating layer located at a lower portion thereof,and thus there is a limit in preventing moisture from being infiltratedinto the pixel region (SP).

SUMMARY

A flexible organic electroluminescent device may include a substratedefined with a display area including a plurality of pixel regions and anon-display area at the outside thereof; a switching thin filmtransistor and a drive thin film transistor formed at the each pixelregion on the substrate; an organic insulating layer deposited on thesubstrate including the switching thin film transistor and drive thinfilm transistor to expose a drain electrode of the drive thin filmtransistor; a first electrode formed in each pixel region on theinorganic insulating layer, and connected to the drain electrode of thedrive thin film transistor; banks formed around each pixel region on thesubstrate including the first electrode and separated from one another;an organic light emitting layer separately formed for each pixel regionon the first electrode; a second electrode formed on an entire surfaceof the display area on the organic light emitting layer; and an organiclayer formed on an entire surface of the substrate including the secondelectrode.

A method of fabricating a flexible organic electroluminescent device mayinclude providing a substrate defined with a display area including aplurality of pixel regions and a non-display area at the outsidethereof; forming a switching thin film transistor and a drive thin filmtransistor at the each pixel region on the substrate; forming an organicinsulating layer on the substrate including the switching thin filmtransistor and drive thin film transistor to expose a drain electrode ofthe drive thin film transistor; forming a first electrode layerconnected to the drain electrode of the drive thin film transistor ineach pixel region on the inorganic insulation; forming banks separatedfrom one another around each pixel region on the substrate including thefirst electrode; forming an organic light emitting layer separately foreach pixel region on the first electrode; forming a second electrode onan entire surface of the display area on the organic light emittinglayer; and forming an organic layer formed on an entire surface of thesubstrate including the second electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a circuit diagram for one pixel region in a typical activematrix type organic electroluminescent device;

FIG. 2 is a plan view schematically illustrating a plurality ofsub-pixel regions of an organic electroluminescent device according tothe related art, as a schematic view showing moisture being infiltratedthrough one sub-pixel region and diffused up to adjoining sub-pixelregions;

FIG. 3 is a schematic cross-sectional view of an organicelectroluminescent device according to the related art;

FIG. 4 is a schematic enlarged cross-sectional view of an organicelectroluminescent device according to the related art, as an enlargedcross-sectional view schematically illustrating moisture infiltratedthrough a bank being diffused along the bank;

FIG. 5 is a plan view schematically illustrating a plurality ofsub-pixel regions of an flexible organic electroluminescent deviceaccording to the present invention, as a view schematically showing thatbanks are separated between each pixel region and thus moisture is notdiffused up to adjoining sub-pixel regions even when the moisture isinfiltrated into one sub-pixel region;

FIG. 6 is a schematic cross-sectional view of a flexible organicelectroluminescent device according to the present invention;

FIG. 7 is a schematic enlarged cross-sectional view of a flexibleorganic electroluminescent device according to the present invention, asan enlarge cross-sectional view schematically illustrating that moistureinfiltrated into one pixel region through the bank is not diffused intoan adjoining pixel region; and

FIGS. 8A through 8J are process cross-sectional views schematicallyillustrating a method of fabricating a flexible organicelectroluminescent device according to the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, an organic electroluminescent device according to preferredembodiments of the present invention will be described below withreference to the accompanying drawings.

FIG. 5 is a plan view schematically illustrating a plurality ofsub-pixel regions of an flexible organic electroluminescent deviceaccording to the present invention, as a view schematically showing thatbanks are separated between each pixel region and thus moisture is notdiffused up to adjoining sub-pixel regions even when the moisture isinfiltrated into one sub-pixel region.

FIG. 6 is a schematic cross-sectional view of a flexible organicelectroluminescent device according to the present invention.

FIG. 7 is a schematic enlarged cross-sectional view of a flexibleorganic electroluminescent device according to the present invention, asan enlarge cross-sectional view schematically illustrating that moistureinfiltrated into one pixel region through the bank is not diffused intoan adjoining pixel region.

A flexible organic electroluminescent device 100 according to anembodiment of the present invention is divided into a top emission typeand a bottom emission type according to the transmission direction ofemitted light, and hereinafter, according to the present invention, thetop emission type will be described as an example.

Referring to FIGS. 5, 6 and 7, in a flexible organic electroluminescentdevice 100 according to the present invention, a substrate 101 formedwith the drive thin film transistor (DTr) and the organic light emittingdiodes (E) is encapsulated by a barrier film (not shown).

Specifically describing the flexible organic electroluminescent device100 according to the present invention, as illustrated in FIG. 6, adisplay area (AA) is defined, and a non-display area (NA) is defined atthe outside of the display area (AA) on the substrate 101, and aplurality of pixel regions (P), each defined as a region surrounded bythe gate line (not shown) and the data line (not shown) are provided,and the power line (not shown) is provided in parallel to the data line(not shown) in the display area (AA).

Here, the flexible substrate 101 is made of a flexible glass substrateor plastic material having a flexible characteristic to maintain displayperformance as it is even when the flexible organic electroluminescentdevice 100 is bent like a paper.

Furthermore, a buffer layer (not shown) made of an insulation material,silicon oxide (SiO₂) or silicon nitride (NiNx), which is an inorganicinsulation material, is provided on the substrate 101. Here, the bufferlayer (not shown) is formed at a lower portion of the semiconductorlayer 103 formed during the subsequent process to prevent thecharacteristics of the semiconductor layer 103 from being deteriorateddue to the emission of alkali ions coming out of an inner portion of thesubstrate 101 during the crystallization of the semiconductor layer 103.

A semiconductor layer 103 made of pure polysilicon to correspond to thedrive region (not shown) and switching region (not shown), respectively,and comprised of a first region 103 a forming a channel at the centralportion thereof and second regions 103 b and 103 c in which a highconcentration of impurities are doped at both lateral surfaces of thefirst region 103 a is formed at each pixel region (P) within the displayarea (AA) at an upper portion of the buffer layer (not shown).

A gate insulating layer 105 is formed on the buffer layer (not shown)including the semiconductor layer 103, and a gate electrode 107 isformed to correspond to the first region 103 a of each of thesemiconductor layer 103 in the drive region (not shown) and switchingregion (not shown) on the gate insulating layer 105.

A gate line (not shown) connected to a gate electrode (not shown) formedin the switching region (not shown) and extended in one direction isformed on the gate insulating layer 105. Here, the gate electrode 107and the gate line (not shown) may have a single layer structure which ismade of a first metal material having a low resistance characteristic,for example, any one of aluminium (Al), aluminium alloy (AlNd), copper(Cu), copper alloy, molybdenum (Mo), and molytitanium (MoTi), or mayhave a double layer or triple layer structure which is made of two ormore of the first metal materials. According to the drawing, it isillustrated that the gate electrode 107 and gate line (not shown) have asingle layer structure.

An interlayer insulating layer 109, which is made of an insulationmaterial, for example, silicon oxide (SiO₂) or silicon nitride (NiNx),which is an inorganic insulation material, is formed on an entiresurface of the display area on the gate electrode 107 and gate line (notshown). Here, a semiconductor layer contact hole (not shown; refer toreference numerals 111 a and 111 b in FIG. 8B) for exposing the secondregions 103 b and 103 c, respectively, located at both lateral surfacesof the first region 103 a of each of the semiconductor layer, isprovided on the interlayer insulating layer 109 and the gate insulatinglayer 105 at a lower portion thereof.

A data line (not shown) crossed with a gate line (not shown) to definethe pixel region (SP) and made of a second metal material, for example,any one or two or more of aluminium (Al), aluminium alloy (AlNd), copper(Cu), copper alloy, molybdenum (Mo), molytitanium (MoTi), chromium (Cr),and titanium (Ti), and a power line (not shown) separated therefrom areformed at an upper portion of the interlayer insulating layer 109including the semiconductor layer contact hole (not shown; refer toreference numerals 111 a and 111 b in FIG. 8B). Here, the power line(not shown) may be formed to be separated from and in parallel to thegate line (not shown) on a layer formed with the gate line (not shown),namely, the gate insulating layer.

A source electrode 113 a and a drain electrode 113 b brought intocontact with the second regions 103 b and 103 c separated from eachother, and respectively exposed through the semiconductor layer contacthole (not shown; refer to reference numerals 111 a and 111 b in FIG. 8B)and formed of the same second metal material as that of the data line(not shown) are formed in the each drive region (not shown) andswitching region (not shown) on the interlayer insulating layer 109.Here, the semiconductor layer and gate insulating layer sequentiallydeposited on the drive region (not shown) and the gate electrode 107 andinterlayer insulating layer 109 and the source electrode 113 a and drainelectrode 113 b formed to be separated from each other forms a drivethin film transistor (DTr).

On the other hand, though it is shown in the drawing that all the dataline (not shown) and source electrode 113 a and drain electrode 113 bhave a single layer structure as an example, the constituent elementsmay have a double layer or triple layer structure.

Here, though not shown in the drawing, a switching thin film transistor(not shown) having the same layer structure as that of the drive thinfilm transistor (DTr) is also formed in the switching region (notshown). Here, the switching thin film transistor (not shown) iselectrically connected to the drive thin film transistor (DTr), the gateline (not shown) and data line 113. In other words, the gate line anddata line 113 are connected to a gate electrode (not shown) and a sourceelectrode (not shown), respectively, of the switching thin filmtransistor (not shown), and the drain electrode (not shown) of theswitching thin film transistor (not shown) is electrically connected tothe gate electrode 107 of the drive thin film transistor (DTr).

According to the substrate 101 for an organic electroluminescent devicein accordance with the present invention, it is shown that the drivethin film transistor (DTr) and switching thin film transistor (notshown) have a semiconductor layer 103 with polysilicon, and configuredwith a top gate type as an example, but it should be understood by thoseskilled in the art that the drive thin film transistor (DTr) andswitching thin film transistor (not shown) can be also configured with abottom gate type having a semiconductor layer with amorphous silicon.

When the drive thin film transistor (DTr) and switching thin filmtransistor (not shown, STr) are configured with a bottom gate type, thelayer structure includes a gate electrode, a gate insulating layer, anactive layer with pure amorphous silicon, semiconductor layers separatedfrom each other and made of an ohmic contact layer having amorphoussilicon doped with impurities, and a source electrode and a drainelectrode separated from each other. Here, it has a characteristic thatthe gate line is formed to be connected to the gate electrode of theswitching thin film transistor on a layer formed with the gateelectrode, and the data line is formed to be connected to the sourceelectrode on a layer formed with the source electrode of the switchingthin film transistor.

An organic insulating layer 115 and an inorganic insulating layer 117having a drain contact hole (not shown; refer to reference numeral 119in FIG. 8D) for exposing the drain electrode 113 b of the drive thinfilm transistor (DTr) is formed on the drive thin film transistor (DTr)and switching thin film transistor (not shown). Here, a high organicmolecular substance such as a polymer is sued for the organic insulatinglayer 115, and silicon oxide (SiO₂) or silicon nitride (NiNx), which isan inorganic insulation material, is used for the inorganic insulatinglayer 117.

A first electrode 121 brought into contact with the drain contact hole(not shown) through the drain electrode 113 b and the drain contact holeof the drive thin film transistor (DTr) and having a separated form foreach pixel region (SP) is formed on the inorganic insulating layer 117.

A bank 123 made of an insulation material, particularly, for example,benzo-cyclo-butene (BCB), polyimide or photo acryl is formed in theboundary and non-display area (NA) of each pixel region (SP) on thefirst electrode 121. Here, a first and a second bank 123 a and 123 bconstituting the bank 123 is formed to be overlapped with the edge ofthe first electrode 121 in the form of surrounding the each pixel region(SP), and the display area (AA) forms a lattice shape having a pluralityof opening portions as a whole.

The banks 123 a and 123 b are formed around each pixel region (SP), andthe banks 123 a and 123 b are formed in a separate manner independentlyfrom each other. In particular, the first banks 123 a and 123 b aroundthe each pixel region (SP) are separated from each other by apredetermined distance. Part of the second bank 123 b is also formed inthe non-display area (NA).

Accordingly, even when a defect or moisture is infiltrated into theorganic electroluminescent device 100 from the outside, the first andsecond banks 123 a and 123 b around each pixel region (SP) areindependently separated from each other, thereby preventing moistureinfiltrated into one pixel region (SP) from being diffused to anotheradjoining pixel region (SP) through the separated bank.

An organic light emitting layer 125 comprised of organic light emittingpatterns (not shown) for emitting red, green and blue colors,respectively, is formed on the first electrode 121 within each of thepixel region (SP) surrounded by the first and second banks 123 a and 123b. The organic light emitting layer 125 may be configured with a singlelayer made of an organic light emitting material, and otherwise, thoughnot shown in the drawing, may be configured with a multiple layer with ahole injection layer, a hole transporting layer, an emitting materiallayer, an electron transporting layer, and an electron injection layer.

A second electrode 127 is formed on an entire surface of the displayarea (AA) at an upper portion of the organic light emitting layer 125and first and second banks 123 a and 123 b. Here, the first electrode121 and second electrode 127 and the organic light emitting layer 125interposed between the two electrodes 121 and 127 form an organic lightemitting diode (E).

For the organic light emitting diode (E), when a predetermined voltageis applied to the first electrode 121 and second electrode 127 accordingto the selected color signal, holes injected from the first electrode121 and electrons provided from the second electrode 127 is transportedto the organic light emitting layer 125 to form excitons, and light isgenerated and emitted in a visible light form when the excitons istransitioned from the excited state to the ground state. At this time,the emitted light is exited to the outside through the transparentsecond electrode 127, and thus the flexible organic electroluminescentdevice 100 implements any image.

A first passivation layer 129 made of an insulation material,particularly, silicon oxide (SiO₂) or silicon nitride (NiNx), which isan inorganic insulation material, is formed on an entire surface of thesubstrate including the second electrode 127. Here, moistureinfiltration to the organic light emitting layer 125 cannot becompletely suppressed by only the second electrode 127, and thus thefirst passivation layer 129 is formed on the second electrode 127 tocompletely suppress moisture infiltration to the organic light emittinglayer 125.

A high organic molecular substance such as a polymer is coated over thefirst passivation layer 129 to form an organic layer 131. Here, olefinpolymers (polyethylene, polypropylene), polyethylene terephthalate(PET), epoxy resin, fluororesin, polysiloxane, and the like may be usedfor the high molecular layer.

A second passivation layer 133 made of an insulation material, forexample, silicon oxide (SiO₂) or silicon nitride (NiNx), which is aninorganic insulation material, is additionally formed on an entiresurface of the substrate including the organic layer 131 to blockmoisture from being infiltrated through the organic layer 131.

Moreover, though not shown in the drawing, an adhesive is located on anentire surface of the substrate including the second passivation layer133 to face a barrier film (not shown) for the encapsulation of theorganic light emitting diode (E), and the adhesive (not shown) made ofany one of a frit having a transparent adhesive characteristic, anorganic insulation material, and a high molecular substance iscompletely glued to the substrate 101 and barrier film (not shown) withno air layer and interposed between the substrate 101 and barrier film(not shown). Here, according to the present invention, a case of using apress sensitive adhesive (PSA) for the adhesive (not shown) will bedescribed as an example.

In this manner, the substrate 101 is fixed to the barrier film (notshown) through the adhesive (not shown) to form a panel state, therebyconfiguring an organic electroluminescent device 100 according to anembodiment of the present invention.

Therefore, according to an organic electroluminescent device inaccordance with an embodiment of the present invention, an inorganicinsulating layer may be additionally formed on an organic insulatinglayer on a substrate including a switching thin film transistor and adrive thin film transistor to cover an edge portion of the organicinsulating layer so as to block a defect or moisture in advance frombeing infiltrated into the organic electroluminescent device, therebyenhancing the life of the organic electroluminescent device.

According to an organic electroluminescent device in accordance with anembodiment of the present invention, banks may be formed in a separatemanner independently from one another around each pixel region toprevent moisture from being diffused into another adjoining pixel regioneven when the defect or moisture is infiltrated into the organicelectroluminescent device from the outside, thereby enhancing thereliability of the panel.

In addition, according to an organic electroluminescent device inaccordance with an embodiment of the present invention, the averageheight of the substrate may be uniformly maintained on the display unitand bezel portion, and also an adhesive, for example, a gluing agent,for adhering the display to an upper substrate, for example, anencapsulation glass substrate, a plastic plate and a polarizer, may beformed in a thin manner, thereby enhancing the reliability of the panel.

A method of fabricating a flexible organic electroluminescent deviceaccording to the present invention will be described below withreference to FIGS. 8A through 8J.

FIGS. 8A through 8J are process cross-sectional views schematicallyillustrating a method of fabricating a flexible organicelectroluminescent device according to the present invention.

As illustrated in FIG. 8A, a substrate 101 having a flexiblecharacteristic defined with a display area (AA) and a non-display area(NA) at the outside of the display area (AA) is prepared. Here, theflexible substrate 101 is made of a flexible glass substrate or plasticmaterial having a flexible characteristic to maintain displayperformance as it is even when the flexible organic electroluminescentdevice 100 is bent like a paper.

Next, a buffer layer (not shown) made of an insulation material, forexample, silicon oxide (SiO₂) or silicon nitride (NiNx), which is aninorganic insulation material, is formed on the substrate 101. Here, thebuffer layer (not shown) is formed at a lower portion of thesemiconductor layer 103 formed during the subsequent process to preventthe characteristics of the semiconductor layer 103 from beingdeteriorated due to the emission of alkali ions coming out of an innerportion of the substrate 101 during the crystallization of thesemiconductor layer 103.

Subsequently, a semiconductor layer 103 made of pure polysilicon tocorrespond to the drive region (not shown) and switching region (notshown), respectively, and comprised of a first region 103 a forming achannel at the central portion thereof and second regions 103 b and 103c in which a high concentration of impurities are doped at both lateralsurfaces of the first region 103 a is formed at each pixel region (P)within the display area (AA) at an upper portion of the buffer layer(not shown).

Subsequently, a gate insulating layer 105 is formed on the buffer layer(not shown) including the semiconductor layer 103, and a gate electrode107 is formed to correspond to the first region 103 a of each of thesemiconductor layer 103 in the drive region (not shown) and switchingregion (not shown) on the gate insulating layer 105.

Here, a gate line (not shown) connected to a gate electrode 107 formedin the switching region (not shown) and extended in one direction isformed on the gate insulating layer 105. Here, the gate electrode 107and the gate line (not shown) may have a single layer structure which ismade of a first metal material having a low resistance characteristic,for example, any one of aluminium (Al), aluminium alloy (AlNd), copper(Cu), copper alloy, molybdenum (Mo), and molytitanium (MoTi), or mayhave a double layer or triple layer structure which is made of two ormore of the first metal materials. According to the drawing, it isillustrated as an example that the gate electrode 107 and gate line (notshown) have a single layer structure.

Next, as illustrated in FIG. 8B, an interlayer insulating layer 109,which is made of an insulation material, for example, silicon oxide(SiO₂) or silicon nitride (NiNx), which is an inorganic insulationmaterial, is formed on an entire surface of the display area on the gateelectrode 107 and gate line (not shown).

Subsequently, the interlayer insulating layer 109 and the gateinsulating layer 105 at a lower portion thereof are selectivelypatterned to form a semiconductor layer contact hole 111 a and 111 b forexposing the second regions 103 b and 103 c, respectively, located atboth lateral surfaces of the first region 103 a of each of thesemiconductor layer.

Next, as illustrated in FIG. 8C, a second metal material layer (notshown) crossed with a gate line (not shown) to define the pixel region(SP) is formed at an upper portion of the interlayer insulating layer109 including the semiconductor layer contact hole 111 a and 111 b.Here, the second metal material layer (not shown) is made of any one ortwo or more of aluminium (Al), aluminium alloy (AlNd), copper (Cu),copper alloy, molybdenum (Mo), molytitanium (MoTi), chromium (Cr), andtitanium (Ti).

Subsequently, the second metal material layer (not shown) is selectivelypatterned to form a data line (not shown) crossed with the gate line(not shown) to define the pixel region (SP), and a power line (notshown) separated therefrom. Here, the power line (not shown) may beformed to be separated from and in parallel to the gate line (not shown)on a layer formed with the gate line (not shown), namely, the gateinsulating layer.

In addition, during the formation of the data line (not shown), a sourceelectrode 113 a and a drain electrode 113 b brought into contact withthe second regions 103 b, 103 c separated from each other, andrespectively exposed through the semiconductor layer contact hole 111 aand 111 b and formed of the same second metal material as that of thedata line (not shown) are formed at the same time in the each driveregion (not shown) and switching region (not shown) on the interlayerinsulating layer 109. Here, the semiconductor layer and gate insulatinglayer sequentially deposited on the drive region (not shown) and thegate electrode 107 and interlayer insulating layer 109 and the sourceelectrode 113 a and drain electrode 113 b formed to be separated fromeach other forms a drive thin film transistor (DTr).

Though it is shown in the drawing that all the data line (not shown) andsource electrode 113 a and drain electrode 113 b have a single layerstructure as an example, the constituent elements may have a doublelayer or triple layer structure.

Here, though not shown in the drawing, a switching thin film transistor(not shown) having the same layer structure as that of the drive thinfilm transistor (DTr) is also formed in the switching region (notshown). Here, the switching thin film transistor (not shown) iselectrically connected to the drive thin film transistor (DTr), the gateline (not shown) and data line 113. In other words, the gate line anddata line 113 are connected to a gate electrode (not shown) and a sourceelectrode (not shown), respectively, of the switching thin filmtransistor (not shown), and the drain electrode (not shown) of theswitching thin film transistor (not shown) is electrically connected tothe gate electrode 107 of the drive thin film transistor (DTr).

On the other hand, according to the substrate 101 for an organicelectroluminescent device in accordance with an embodiment of thepresent invention, it is shown that the drive thin film transistor (DTr)and switching thin film transistor (not shown) have a semiconductorlayer 103 with polysilicon, and configured with a top gate type as anexample, but it should be understood by those skilled in the art thatthe drive thin film transistor (DTr) and switching thin film transistor(not shown) can be also configured with a bottom gate type having asemiconductor layer with amorphous silicon.

When the drive thin film transistor (DTr) and switching thin filmtransistor (not shown, STr) are configured with a bottom gate type, thelayer structure includes a gate electrode, a gate insulating layer, anactive layer with pure amorphous silicon, semiconductor layers separatedfrom each other and made of an ohmic contact layer having amorphoussilicon doped with impurities, and a source electrode and a drainelectrode separated from each other. Here, it has a characteristic thatthe gate line is formed to be connected to the gate electrode of theswitching thin film transistor on a layer formed with the gateelectrode, and the data line is formed to be connected to the sourceelectrode on a layer formed with the source electrode of the switchingthin film transistor.

Next, an organic insulating layer 115 and an inorganic insulating layer117 are sequentially deposited on the drive thin film transistor (DTr)and switching thin film transistor (not shown). Here, a high organicmolecular substance such as a polymer is sued for the organic insulatinglayer 115, and silicon oxide (SiO₂) or silicon nitride (NiNx), which isan inorganic insulation material, is used for the inorganic insulatinglayer 117.

Subsequently, as illustrated in FIG. 8D, the organic insulating layer115 and inorganic insulating layer 117 are selectively patterned to forma drain contact hole 119 for exposing the drain electrode 113 b of thedrive thin film transistor (DTr).

Next, as illustrated in FIG. 8E, a third metal material layer (notshown) is deposited on the inorganic insulating layer 117, and then thethird metal material layer (not shown) is selectively patterned to forma first electrode 121 brought into contact with the drain contact hole(not shown) through the drain electrode 113 b and the drain contact holeof the drive thin film transistor (DTr) and having a separated form foreach pixel region (SP) is formed through the drain contact hole 119.Here, the third metal material layer (not shown) is made of any one ortwo or more of aluminium (Al), aluminium alloy (AlNd), copper (Cu),copper alloy, molybdenum (Mo), molytitanium (MoTi), chromium (Cr), andtitanium (Ti).

Subsequently, though not shown in the drawing, an insulation materiallayer (not shown) made of benzo-cyclo-butene (BCB), polyimide or photoacryl, for example, is formed in the boundary and non-display area (NA)of each pixel region (SP) on the first electrode 121.

Next, as illustrated in FIG. 8F, the insulation material layer (notshown) is selectively patterned to form a bank 123 including a first anda second bank 123 a and 123 b. Here, the first and second banks 123 aand 123 b are formed to be overlapped with the edge of the firstelectrode 121 in the form of surrounding the each pixel region (SP), andthe display area (AA) forms a lattice shape having a plurality ofopening portions as a whole.

Furthermore, part of the second bank 123 b is formed with a shape thatcovers part of the upper portion of the non-display area (NA). The firstand second banks 123 a and 123 b are formed around each pixel region(SP), and the first and second banks 123 a and 123 b are formed in aseparate manner independently from each other. In particular, the banks123 a and 123 b around the each pixel region (SP) are separated fromeach other by a predetermined distance.

Accordingly, even when a defect or moisture is infiltrated into theorganic electroluminescent device 100 from the outside, the first andsecond banks 123 a and 123 b around each pixel region (SP) areindependently separated from each other, thereby preventing moistureinfiltrated into one pixel region (SP) from being diffused to anotheradjoining pixel region (SP) through the separated bank.

Subsequently, as illustrated in FIG. 8G, an organic light emitting layer125 comprised of organic light emitting patterns (not shown) foremitting red, green and blue colors, respectively, is formed on thefirst electrode 121 within each of the pixel region (SP) surrounded bythe first and second banks 123 a and 123 b. Here, the organic lightemitting layer 125 may be configured with a single layer made of anorganic light emitting material, and otherwise, though not shown in thedrawing, may be configured with a multiple layer with a hole injectionlayer, a hole transporting layer, an emitting material layer, anelectron transporting layer, and an electron injection layer.

Next, as illustrated in FIG. 8H, a second electrode 127 is formed on anentire surface of the display area (AA) including an upper portion ofthe organic light emitting layer 125 and first and second banks 123 aand 123 b. Here, a transparent conductive material for transmittinglight, for example, any one of conductive materials including ITO andIZO may be selected and used for the second electrode 127. In thismanner, the first electrode 121 and second electrode 127 and the organiclight emitting layer 125 interposed between the two electrodes 121 and127 form an organic light emitting diode (E).

Accordingly, for the organic light emitting diode (E), when apredetermined voltage is applied to the first electrode 121 and secondelectrode 127 according to the selected color signal, holes injectedfrom the first electrode 121 and electrons provided from the secondelectrode 127 is transported to the organic light emitting layer 125 toform excitons, and light is generated and emitted in a visible lightform when the excitons is transitioned from the excited state to theground state. At this time, the emitted light is exited to the outsidethrough the transparent second electrode 127, and thus the flexibleorganic electroluminescent device 100 implements any image.

Subsequently, as illustrated in FIG. 8I, a first passivation layer 129made of an insulation material, particularly, silicon oxide (SiO₂) orsilicon nitride (NiNx), which is an inorganic insulation material, isformed on an entire surface of the substrate including the secondelectrode 127. Here, moisture infiltration to the organic light emittinglayer 125 cannot be completely suppressed by only the second electrode127, and thus the first passivation layer 129 is formed on the secondelectrode 127 to completely suppress moisture infiltration to theorganic light emitting layer 125.

Next, as illustrated in FIG. 8J, a high organic molecular substance suchas a polymer is coated over the first passivation layer 129 to form anorganic layer 131. Here, olefin polymers (polyethylene, polypropylene),polyethylene terephthalate (PET), fluororesin, polysiloxane, epoxyresin, and the like may be used for the high molecular layer.

Subsequently, a second passivation layer 133 made of an insulationmaterial, for example, silicon oxide (SiO₂) or silicon nitride (NiNx),which is an inorganic insulation material, is additionally formed on anentire surface of the substrate including the organic layer 131 to blockmoisture from being infiltrated through the organic layer 131.

Next, though not shown in the drawing, an adhesive is located on anentire surface of the substrate including the second passivation layer133 to face a barrier film (not shown) for the encapsulation of theorganic light emitting diode (E), and the adhesive (not shown) made ofany one of a frit having a transparent adhesive characteristic, anorganic insulation material, and a high molecular substance isinterposed between the substrate 101 and barrier film (not shown), andcompletely glued to the substrate 101 and barrier film (not shown) withno air layer. Here, according to the present invention, a case of usinga press sensitive adhesive (PSA) for the adhesive (not shown) will bedescribed as an example.

In this manner, the substrate 101 is fixed to the barrier film (notshown) through the adhesive (not shown) to form a panel state, therebycompleting the fabrication process of an organic electroluminescentdevice 100 according to the present invention.

Therefore, according to a method of fabricating an organicelectroluminescent device in accordance with an embodiment of thepresent invention, an inorganic insulating layer may be additionallyformed on an organic insulating layer on a substrate including aswitching thin film transistor and a drive thin film transistor to coveran edge portion of the organic insulating layer so as to block a defector moisture in advance from being infiltrated into the organicelectroluminescent device, thereby enhancing the life of the organicelectroluminescent device.

Furthermore, according to a method of fabricating an organicelectroluminescent device in accordance with an embodiment of thepresent invention, banks may be formed in a separate mannerindependently from one another around each pixel region to preventmoisture from being diffused into another adjoining pixel region evenwhen the defect or moisture is infiltrated into the organicelectroluminescent device from the outside, thereby enhancing thereliability of the panel.

In addition, according to a method of fabricating an organicelectroluminescent device in accordance with an embodiment of thepresent invention, the average height of the substrate may be uniformlymaintained on the display unit and bezel portion, and also an adhesive,for example, a gluing agent, for adhering the display to an uppersubstrate, for example, an encapsulation glass substrate, a plasticplate and a polarizer, may be formed in a thin manner, thereby enhancingthe reliability of the panel.

However, it may be understood by those skilled in the art that theforegoing present invention can be implemented in other specific formswithout changing the technical concept and essential characteristicsthereof.

Therefore, it should be understood that the foregoing embodiments aremerely illustrative but not restrictive in all aspects. The scope of thepresent invention is defined by the appended claims rather than by thedetailed description, and all changes or modifications derived from themeaning, scope and equivalent concept of the claims should be construedto be embraced by the scope of the present invention.

What is claimed is:
 1. A flexible organic electroluminescent device, comprising: a substrate having a display area including a plurality of pixel regions and a non-display area at the outside thereof; a switching thin film transistor and a drive thin film transistor at each pixel region on the substrate; an organic insulating layer on the substrate including the switching thin film transistor and drive thin film transistor to expose a drain electrode of the drive thin film transistor; a first electrode in each pixel region on the inorganic insulating layer, and connected to the drain electrode of the drive thin film transistor; banks around each pixel region on the substrate including the first electrode and separated from one another; an organic light emitting layer separately formed for each pixel region on the first electrode; a second electrode on an entire surface of the display area on the organic light emitting layer; and an organic layer on an entire surface of the substrate including the second electrode.
 2. The flexible organic electroluminescent device of claim 1, further comprising: a barrier film located to face the substrate; and an adhesive interposed between the substrate and barrier film to adhere the substrate to the barrier film so as to implement a panel state.
 3. The flexible organic electroluminescent device of claim 1, wherein the bank is around each pixel region, and banks at each pixel region are separated independently from one another.
 4. The flexible organic electroluminescent device of claim 1, wherein an inorganic insulating layer is on the organic insulating layer.
 5. The flexible organic electroluminescent device of claim 1, wherein the substrate is configured with one selected from a flexible glass substrate and a plastic material.
 6. The flexible organic electroluminescent device of claim 1, wherein a passivation layer is at an upper and a lower portion of the organic layer, respectively.
 7. A method of fabricating a flexible organic electroluminescent device, the method comprising: providing a substrate defined with a display area including a plurality of pixel regions and a non-display area at the outside thereof; forming a switching thin film transistor and a drive thin film transistor at the each pixel region on the substrate; forming an organic insulating layer on the substrate including the switching thin film transistor and drive thin film transistor to expose a drain electrode of the drive thin film transistor; forming a first electrode layer connected to the drain electrode of the drive thin film transistor in each pixel region on the inorganic insulation; forming banks separated from one another around each pixel region on the substrate including the first electrode; forming an organic light emitting layer separately for each pixel region on the first electrode; forming a second electrode on an entire surface of the display area on the organic light emitting layer; and forming an organic layer formed on an entire surface of the substrate including the second electrode.
 8. The method of claim 7, further comprising: forming a barrier film located to face the substrate; and forming an adhesive interposed between the substrate and barrier film to adhere the substrate to the barrier film so as to implement a panel state.
 9. The method of claim 7, wherein the bank is formed around each pixel region, and banks formed at each pixel region are separated independently from one another.
 10. The method of claim 7, wherein an inorganic insulating layer is additionally formed on the organic insulating layer.
 11. The method of claim 7, wherein the substrate is configured with one selected from a flexible glass substrate and a plastic material.
 12. The method of claim 7, wherein a passivation layer is formed at an upper and a lower portion of the organic layer, respectively. 